Well I tried to stay out of it but this chip programming just looks like too much fun. The EBL Flash looks real slick and one is probably in my future but for now I decided to get my feet wet hacking on my '91 Caprice wagon ECM, which I had put a commercial chip into.

I realized I had an old PROM burner kicking around from a long dead project and I read in the stock chip and started studying it in TunerPro and was pretty impressed by that software, pretty slick.

Wow, I've got to see what the differences are on the commercial chip, lets pop it out in put it in the reader. Man, the plastic holders for the 2732A chips from my ECM are a pain, I got the chip out but mangled 2 pins pretty bad, geez, nice start to my new career. One pin straightened out ok but the other one was just about to crack off after straightening.

Yikes, I don't think I can come up with a believable story to give the chip company on why I was taking the chip out of holder and mangled it and need a replacement, but fortunately the bad pin hung on long enough to be able to read the chip on the burner.

Pretty interesting to look at compared to the stock chip (the Compare function in TunerPro is nice), mostly just more timing and fuel, but it does run a lot better. However, no way the mangled pin was going to survive another insertion.

Hey no problem, I live close to Jameco, I'll just run down and pick up some chips, I'll get 5 to have some spares. No go, every chip burn failed at a different place on the verify. From what I understand, these old 2732A chips can be troublesome, so I guess I got a bad batch or maybe have a problem with the programmer. I'll pop the stock chip back in for now and try some chips from a different source.

What I found on the 2732A holders it that the best way to get a chip out is to pop off the plastic ribs and end pieces that hold the chip in on the top and then the chip pushes out easily from the bottom. You can still use the holders, just insert the chip from the bottom till the pins go in the recesses and then put your thumb on the top of the chip when putting it in the socket.

I've spent a fair amount of time looking at links in the forum to get a background on tuning and have a couple of questions.

The BPW Constant in my $62 '91 Caprice bin is a multiplicative constant that effects all the fuel settings, correct? In other words, if I were to put in injectors that were rated for twice as much fuel, if you set the BPW Constant to 1/2 its current setting, in theory the amount of fuel delivered in all conditions would be the same, correct?

Looking at the .bin for the EBL I didn't see the BPW Constant, how is that function handled in the EBL .bin?

Which wideband O2 sensor do you guys like the best, the first one I've seen is this one ( www.zeitronix.com ) and it looks pretty nice, are there others I should look at?

Thanks,

Paul T.

 

It is, and easy to get addicted too.

Can I use 'it is' again?.

The Zeitronix and Innovate units (LM-1 & LC-1) are the two most popular WB units here. There are others out there but don't hear much of them.

For the BPW (also called the BPC, base pulse constant) it is the engine displacement and injector flow rolled into one.

BPC = 1461.5 * (VOL/RATE)
VOL = Vol of 1 Cylinder in liters, (0.7125l for 350)
RATE = Injector flow in gms/sec


In the EBL there is a table of BPC vs VAC. It is done this way so that a vacuum referenced fuel pressure regulator may be used. Which in turn allows for higher fuel pressure under load, and a lower fuel pressure under lighter load. This makes it easier to tune for a higher injector flow rate.

The BPC doesn't affect AE, so that will need to be changed if the injector flow is changed.

RBob.